Tissue-Specific Alteration of Metabolic Pathways Influences Glycemic Regulation

Metabolic dysregulation in multiple tissues influences risk for type 2 diabetes (T2D). To identify pathways and tissues influencing T2D-relevant glycemic traits we investigated associations of exome-array variants in up to 144,060 nondiabetic individuals of multiple ancestries. Single-variant analyses identified 21 novel coding variant associations (18 loci), whilst gene-based tests revealed novel signals at TF (HbA1c) and G6PC [(Fasting Glucose (FG), Fasting Insulin (FI)]. Pathway and tissue enrichment analyses of trait-associated transcripts confirmed the importance of liver and kidney for FI and islets for FG, implicated adipose tissue in FI and gut in 2hGlu, and a role for the non-endocrine pancreas in glucose homeostasis. Functional studies demonstrated that the liver-enriched G6PC and the islet-specific G6PC2 were driven by multiple rare variants, with G6PC2 including two alleles within the same codon with divergent effects on glucose levels. Our findings highlight the value of integrating genomic and functional data to maximize biological inference.